1. Technical Field
The present invention relates to a manufacturing method of a semiconductor device for processing a substrate having a high dielectric gate insulating film and a metal electrode, and a substrate processing apparatus.
2. Description of Related Art
In recent years, with high integration and high speed of a semiconductor device, a finer transistor and a thinner film are being developed. When the thinner film of a gate insulating film is progressed by this finer transistor, leak current of the gate electrode due to tunnel current, etc, is increased in a silicon oxide film (SiO2 film) that has been used heretofore as the gate insulating film. Particularly, the gate insulating film does not function as an insulating film when the leak current is increased, unlike a capacitor insulating film, and therefore the leak current must be suppressed. Also, in the gate electrode, it is necessary to make electricity resistance small, increase conductivity, and accelerate operation characteristics. Therefore, study on the semiconductor device, with the gate insulating film made of a high dielectric material and the gate electrode made of metal, is being pursued. The gate insulating film made of a high dielectric material is called a high dielectric also called High-k gate insulating film, and the gate electrode made of metal is called a metal electrode hereinafter.
FIG. 9 shows main steps and typical processing contents of a process flow of a MOS transistor. In order to manufacture the MOS transistor, first, the gate insulating film is formed using the high dielectric material such as HfO and HfSiO on a silicon substrate (gate insulating film forming step).
Next, the gate electrode is formed using a metal material such as tungsten(W), ruthenium(Ru), titanium nitride(TiN), tantalum(Ta), molybdenum(Mo) instead of conventional polysilicon (gate electrode forming step).
Subsequently, processing of the gate electrode and the gate insulating film is performed by dry etching, through formation and processing of an etching mask (etching step). Thereafter, an etching damage of the gate electrode, namely, a physical roughness of a processing surface generated by etching is restored by thermal oxidation (restoration step of the gate electrode). When the restoration step is ended, ion implantation is performed to the surface of the silicon substrate, to thereby form source and drain. Subsequently, dopant (phosphorus (P), arsenic (As), and boron (B), etc, implanted to channel, source, and drain) is activated by annealing.
However, when the gate electrode is made of metal, the gate electrode is excessively oxidized in the restoration step of the gate electrode, and a resistance value is increased in some cases by oxidation.
As a method of suppressing excessive oxidation of the gate electrode, a method of reducing oxidation of the gate electrode by using hydrogen as a reducing agent, in a processing pressure of mixed gas of oxygen gas and hydrogen gas, with a temperature of the silicon substrate set to be a prescribed temperature of 850° C. or more, can be considered.
However, high dielectric materials such as hafnium (HfO), hafnium silicate (HfSiOx, also called HfSiO hereunder), hafnium nitride silicate (HfSiON), and aluminum oxide (AlOx) are sometimes crystallized, for example, by a thermal history of about 400° C. to 1000° C. Accordingly, when the silicon substrate is heated as described above to 850° C. or more, a High-k gate insulating film made of high dielectric material is sometimes formed into a polycrystal structure. A crystal grain boundary exists in the High-k gate insulating film having polycrystal structure, and therefore current flows through defects of the crystal grain boundary when a voltage is applied to the gate electrode, resulting in an increase of leak current.